Re: Bug in collation functions?

[Ken Brown <kbrown@cornell.edu>]

On 10/29/2015 11:35 AM, Corinna Vinschen wrote:
> On Oct 29 08:59, Ken Brown wrote:
>> On 10/29/2015 4:30 AM, Corinna Vinschen wrote:
>>> On Oct 29 08:50, Corinna Vinschen wrote:
>>>> On Oct 28 21:58, Eric Blake wrote:
>>>>> On 10/28/2015 04:14 PM, Ken Brown wrote:
>>>>>> It's my understanding that collation is supposed to take whitespace and
>>>>>> punctuation into account in the POSIX locale but not in other locales.
>>>>>
>>>>> Not quite right. It is up to the locale definition whether whitespace
>>>>> affects collation.  But you are correct that in the POSIX locale,
>>>>> whitespace must not be ignored in collation.
>>>>>
>>>>>> This doesn't seem to be the case on Cygwin.  Here's a test case using
>>>>>> wcscoll, but the same problem occurs with strcoll.
>>>>>
>>>>> That's because the locale definitions are different in cygwin than they
>>>>> are in glibc.  But it is not a bug in Cygwin; POSIX allows for different
>>>>> systems to have different locale definitions while still using the same
>>>>> locale name like en_US.UTF-8.
>>>>
>>>> Btw, strcoll and wcscoll in Cygwin are implemented using the Windows
>>>> function CompareStringW with the LCID set to the locale matching the
>>>> POSIX locale setting.  I'm rather glad I didn't have to implement this
>>>> by myself... :}
>>>
>>> OTOH, CompareString has a couple of flags to control its behaviour, see
>>> https://msdn.microsoft.com/en-us/library/windows/desktop/dd317761%28v=vs.85%29.aspx
>>>
>>> Right now Cygwin calls CompareStringW with dwCmpFlags set to 0, but there
>>> are flags like NORM_IGNORENONSPACE, NORM_IGNORESYMBOLS.  I'm open to a
>>> discussion how to change the settings to more closely resemble the rules
>>> on Linux.
>>>
>>> E.g.  wcscoll simply calls wcscmp rather than CompareStringW for the
>>> C/POSIX locale anyway.  So, would it makes sense to set the flags to
>>> NORM_IGNORESYMBOLS in other locales?
>>
>> I think so.  That's what the native Windows build of emacs does in this
>> situation.
>
> Is that all it's doing?  I'm asking because using NORM_IGNORESYMBOLS
> does not exaclty resemble the behaviour on Linux on my W10 box:
>
>      "11" > "1.1" in POSIX locale
> !!! "11" > "1.1" in en_US.UTF-8 locale
>      "11" > "1 2" in POSIX locale
>      "11" < "1 2" in en_US.UTF-8 locale

I just noticed that myself and was going to ask about that difference. 
I don't see anything else that emacs is doing on native Windows.  But in 
the test I referred to above, the locale is set to "enu_USA" in the 
native Windows build.  Does that explain the discrepancy?  If not, I can 
ask on the emacs-devel list whether the test passes on Windows.

Ken

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